im not sure if this applies to your diff, but i tried installing a quaife lsd in a customers car, it got it to go in but the way it was build and not able to shim the bmw diff, it had the ring gear way to tight against the pinion gear so there was zero backlash, needless to say i would not leave it in, i pulled it back out and put the stock back in

Good move.

I've changed ring and pinions on v8 American cars and seen plenty of others installed by so-so shops and the backlash AND pinion depth has to be perfect or it will whine (or worse).

The ol' magnetic mount dial indicator (to measure backlash) as well as some test turning of the assembly to note the pattern of the ring and pinion gear contact area is required.

My 2c is that I'd never take a car to have a ring and pinion swapped unless a) they do a LOT of R&P gear swaps on various cars or b) they've actually done at least one R&P swap on the exact scenario/car I would be leaving with them.

I've changed ring and pinions on v8 American cars and seen plenty of others installed by so-so shops and the backlash AND pinion depth has to be perfect or it will whine (or worse).

The ol' magnetic mount dial indicator (to measure backlash) as well as some test turning of the assembly to note the pattern of the ring and pinion gear contact area is required.

My 2c is that I'd never take a car to have a ring and pinion swapped unless a) they do a LOT of R&P gear swaps on various cars or b) they've actually done at least one R&P swap on the exact scenario/car I would be leaving with them.

yea i have done plenty of american cars that can actually be adjusted by shimming, the bmw cant be shimmed, if i left it in it would have lasted a week tops before eating up the ring gear or snapping the pinion, it was tight as can be

im not sure if this applies to your diff, but i tried installing a quaife lsd in a customers car, it got it to go in but the way it was build and not able to shim the bmw diff, it had the ring gear way to tight against the pinion gear so there was zero backlash, needless to say i would not leave it in, i pulled it back out and put the stock back in

BMW shims for the differential are a bitch to get. Unfortunately there are a limited # of shops that have access to the parts to do this job properly.

A long time ago, when I looked into swapping the different BMW LSDs into a 335, I couldn't find a good fit. I don't have access to a shop that can do the driveline work that George was able to get done.

At this point it would be great if we could get one of the shops like KMS or Metric Mechanics to discuss the details of what is involved with this swap. Drivelines are not easy to mess with, the tolerances are very, very, precise, nothing can be out of balance or too short or long.

The strange thing with my Quaife installation was there was zero wine or any type of noise. It seemed quieter than stock.
I took it to the drags and after eight burn outs it was whining like a swine with flu. The wine would come and go on light pedal on or off. The higher the speed the louder the whine.

For those that asked the two pieces of the driveshafts bolted directly with no mods.

The strange thing with my Quaife installation was there was zero wine or any type of noise. It seemed quieter than stock.
I took it to the drags and after eight burn outs it was whining like a swine with flu. The wine would come and go on light pedal on or off. The higher the speed the louder the whine.

For those that asked the two pieces of the driveshafts bolted directly with no mods.

Just to clarify though, the driveshafts bolted up with no issue but you did have to cut one of them (assuming to shorten it?), and hence you had to re-balance the drive shaft?

Or did you mean that after you bolted the 2 driveshafts together, you re-balanced it then anyway - which is probably a good idea.

I remember you mentioning that with the shorter ratio you could not get the traction down. I had the same problems with the M3 diff but what I did is a tuned in a far less aggressive boost map, stepping it up very gradually and it seems to have done the trick in terms of traction.

I'm impressed you remember my comment so long ago...

Well, the prespective of using an /M diff in a non-M car is really interesting but using a shorter final drive ratio is mistaken (in my opinion ,of course).

There is no need to use a shorter final drive when you have a car that performs the +50% of its maximum torque from 1200revs ,like 335i.
A shorter diff would be ideal for the naturaly aspirated //M cars that needs to reach their beneficial rev range fast (which is pretty high at 5500revs+).

Again, I find impressive your whole experiment from a technical view, but in your place i would roll back to your quaife one

Well, the prespective of using an /M diff in a non-M car is really interesting but using a shorter final drive ratio is mistaken (in my opinion ,of course).

There is no need to use a shorter final drive when you have a car that performs the +50% of its maximum torque from 1200revs ,like 335i.
A shorter diff would be ideal for the naturaly aspirated //M cars that needs to reach their beneficial rev range fast (which is pretty high at 5500revs+).

Again, I find impressive your whole experiment from a technical view, but in your place i would roll back to your quaife one

I remembered your comment as you said traction was a issue.
I think at this stage the diff is much to short, when bigger turbos come it will be beneficial in my case. I am not sure if you have driven a automatic car with lag. The first few rpms seem like a lifetime. Then there will be a benefit. Further than that I think I can pull away in second and still maintain the same rate of acceleration as using both gears with OEM final drive. Then 3, 4, 5 and 6th are crazy because the car has to pull through a much shorter gear.
Another advantage is that at the moment I have a choice of eight final drive ratios available after market with a zip of my credit card. With the OEM diff I have none or maybe 1 if I can find a manual diff which isn't welded.

Well, the prespective of using an /M diff in a non-M car is really interesting but using a shorter final drive ratio is mistaken (in my opinion ,of course).

There is no need to use a shorter final drive when you have a car that performs the +50% of its maximum torque from 1200revs ,like 335i.
A shorter diff would be ideal for the naturaly aspirated //M cars that needs to reach their beneficial rev range fast (which is pretty high at 5500revs+).

Again, I find impressive your whole experiment from a technical view, but in your place i would roll back to your quaife one

I 100% agree with you, which is why I chose to stick with the 3.08. If I had a chance to go taller then I would have.

im not sure if this applies to your diff, but i tried installing a quaife lsd in a customers car, it got it to go in but the way it was build and not able to shim the bmw diff, it had the ring gear way to tight against the pinion gear so there was zero backlash, needless to say i would not leave it in, i pulled it back out and put the stock back in

I could be wrong but I believe there are two versions of the Quaife on the market, cars with newer build dates have a smaller pumpkin and therefor use a newer/smaller Quaife LSD.. maybe this is the reason for the tight fit

I
Another advantage is that at the moment I have a choice of eight final drive ratios available after market with a zip of my credit card. With the OEM diff I have none or maybe 1 if I can find a manual diff which isn't welded.

Where do you find other final drives? I am going that route but before starting I really need to find a final drive of lets say 3.2

I could be wrong but I believe there are two versions of the Quaife on the market, cars with newer build dates have a smaller pumpkin and therefor use a newer/smaller Quaife LSD.. maybe this is the reason for the tight fit

that announcement came out a week after trying to install it in the car lol, i was told the diff case needed to be grinded and all but i wasnt buying it, i wasnt leaving it installed and letting a perfectly good ring and pinion get destroyed

You can search on the M3post. Dinan, Evosport, diffsonline and the OEM 3.15 that I can think of from the top of my head.

where to find the OEM 3.15 one at a reasonable price?
as far as I understood the single parts aren't available by BMW, only the complete diff. Unfortunatelly I found only a normal 3.85 M3 6MT diff at the scrap complete with all the subframe, harms, brakes and half shafts..

where to find the OEM 3.15 one at a reasonable price?
as far as I understood the single parts aren't available by BMW, only the complete diff. Unfortunatelly I found only a normal 3.85 M3 6MT diff at the scrap complete with all the subframe, harms, brakes and half shafts..

I know two people that have installed the Dinan 3.62 and have the 3.15 sitting. Their prices are unreasonable at the moment but I am sure soon the used market will have plenty for cheap.

I think its essential that everyone researches M3 diffs as I know of a few people that have had to swop theirs out under warranty. So it might sound exciting and all but is the diff superior to a OEM 335 with a LSD.